Hanson is set to write to its ready-mix customers asking that concrete is not specified with a GGBS (ground granulated blast furnace slag) content of more than 40%, according to reports from Contract Journal, UK.
When cement shortages began to bite, the company started receiving requests for an increased GGBS content to make the available cement go further. This has led to a shortage of GGBS, while cement supplies have now eased.
Its ready-mix concrete is usually supplied with a GGBS content of between 30% and 50%, but some have been asking for up to 70%.
A Hanson spokesman told CJ: "The requests for increased GGBS content in concrete has been putting pressure on us and now supplies are running low.
"We will now be writing to customers asking that they do not specify more than 40%. It is preferable to do that rather than ration or allocate."
The spokesman said he was confident that supplies will back on track by the end of June.